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Data Communications Networks
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- Navigate this page:
- The Internet and the World Wide Web
- The Technology of the Web
- Intranets and Extranets
15.5 Data Communications NetworksLEARNING OBJECTIVE
In addition to using networks for information sharing within the organization, companies use networks to communicate and share information with those outside the organization. All this is made possible by data communication networks, which transmit digital data (numeric data, text, graphics, photos, video, and voice) from one computer to another using a variety of wired and wireless communication channels. Let’s take a closer look at the networking technologies that make possible all this electronic communication—in particular, the Internet (including the World Wide Web),intranets, and extranets. The Internet and the World Wide WebThough we often use the terms Internet and World Wide Web interchangeably, they’re not the same thing. [1] The Internet is an immense global network comprising smaller interconnected networks linking millions of computers around the world. Originally developed for the U.S. military and later adapted for use in academic and government research, the Internet experienced rapid growth in the 1990s, when companies called Internet service providers were allowed to link into the Internet infrastructure in order to connect paying subscribers. Today, Internet service providers, such as CompuServe, America Online (AOL), MSN, and Comcast, enable us to use the Internet to communicate with others through e-mail, texting, instant messaging, online conferencing, and so on. These services also connect us with third-party providers of information, including news stories, stock quotes, and magazine articles. The World Wide Web (or simply “the Web”) is just a portion of the Internet—albeit a large portion. The Web is a subsystem of computers that can be accessed on the Internet using a special protocol, or language, known as hypertext transfer protocol (HTTP). What’s the difference between the Internet and the Web? According to Tim Berners-Lee (one of the small team of scientists who developed the concept for the Web in 1989), the Internet is a network of networks composed of cables and computers. You can use it to send “packets” of information from one computer to another, much like sending a postcard. If the address on the packet is accurate, it will arrive at the correct destination in much less than a second. Thus, the Internet is a packet-delivery service that delivers such items as e-mail messages all over the globe. The Web, by contrast, is composed of information—documents, pictures, sounds, streaming videos, and so on. It’s connected not through cables, but rather through hypertext links that allow users to navigate between resources on the Internet. [2] Because it’s driven by programs that communicate between computers connected to the Internet, the Web couldn’t exist without the Internet. The Internet, on the other hand, could exist without the Web, but it wouldn’t be nearly as useful. The Internet itself is enormous, but it’s difficult to navigate, and it has no pictures, sounds, or streamed videos. They exist on computers connected to the Web, which also makes it much easier to retrieve information. The creation of Web browsers—software, such as Microsoft’s Internet Explorer and Netscape Navigator, that locates and displays Web pages—opened up the Internet to a vast range of users. Almost 80 percent of individuals in the United States use the Internet regularly. [3] So, who’s in charge of the Web? No one owns it, but an organization called the World Wide Web Consortium (W3C) oversees the development and maintenance of standards governing the way information is stored, displayed, and retrieved on it. [4] The Technology of the WebFigure 15.8 Google 
Let’s look a little more closely at some of the technologies that enable us to transmit and receive data over the Web. Documents on the Web are called Web pages, and they’re stored on Web sites. Each site is maintained by a Webmaster and opens with a home page. Each Web page is accessed through a unique address called a uniform resource locator (URL). For example, if you want to find statistics on basketball star LeBron James, you could type in the URL address http://www.nba.com/home/playerfile/lebron_james. The prefixhttp:// is the protocol name, http://www.nba.com the domain name, playerfile the subdirectory name, and lebron_james the document name (or Web page). A computer that retrieves Web pages is called a Web server. A search engine is a software program that scans Web pages containing specified keywords and provides a list of documents containing them. The most popular search engine is Google; others include Bing, Yahoo!, Ask, and AOL. Intranets and ExtranetsWhat’s the difference among the Internet, an intranet, and an extranet? It depends on who can and can’t access the information on the network. The Internet is a public network that anyone can use. A company’s intranet, on the other hand, is a private network using Internet technologies that’s available only to employees; access is controlled by a software program called a firewall. The information available on an intranet varies by company but may include internal job postings, written company policies, and proprietary information, such as price lists meant for internal use only. An extranet is an intranet that’s partially available to certain parties outside the organization. Say, for example, you’ve posted the following information on your intranet: company policies, payroll and benefit information, training programs, parts specifications and inventories, and production schedules. To allow suppliers to bid on contracts, you might give them access to sections of the site disclosing parts specifications, inventories, and production schedules. All other sections would be off limits. You’d control access to employee-only and supplier-accessible sections by means of usernames and passwords. As you can see from Figure 15.9 "How an Extranet Works", which illustrates some of the connections made possible by an extranet, access can be made available to customers and business partners, as well. Figure 15.9 How an Extranet Works 
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